This project seeks to define the role of certain neural connectivity patterns in the elaboration of (1) the complex topographic arrangement of neurons belonging to different submodality classes at rostral levels of the somatic sensory system; and (2) the highly "tuned" response properties displayed by the first-order and cerebral cortical neurons which receive the projections from low-threshold mechanoreceptors in the hairy skin of primates. The experiments which are proposed require the employment of (1) the techniques of extracellular recording with microelectrodes; (2) computer-aided neural data analysis techniques; (3) rigidly controlled and monitored mechanical stimuli; (4) aseptic neurosurgical procedures; (5) characterization of the anatomical extent of the lesion produced by the neurosurgical operative procedures; and (6) precise reconstruction of the microelectrode tracks by means of the identification of microlesions in stained serial sections of the appropriate level of the somatic sensory system. It is anticipated that the data obtained will extend current views of information processing in sensory systems and will lead to behavioral and clinical research designed to re-evaluate the functional deficits which result from selective damage of a variety of levels of the primate somatic sensory system.